1. Field of the Invention
The present invention relates to a water-based ink composition, and more particularly to one for a ball-point pen, which enables a ball seat of the pen to be substantially protected from wearing caused by the rotation of a ball of the pen so as to keep good ink-discharging properties of the pen.
2. Description of the Prior Art
In conventional water-based inks for ball-point pens, water-soluble dyes such as direct dyes, acid dyes, basic dyes and the like acting as colorants are dissolved in aqueous solutions of water-soluble organic solvents such as glycols, glycol ethers, glycol ether esters, amines and the like acting as evaporation inhibitors, in which inks further optionally dissolved are preservatives, anion or nonion surface-active agents and the like, as is well known. In the inks, organic or inorganic pigments may be employed as the colorants, and in this case dispersants are usually employed together with such colorants for dispersing the pigments in a stable manner.
However, in comparison with an oil-based ink having a large viscosity and acting as a lubricant, in case of the water-based ink being employed in the ball-point pen, there is a tendency to wear out the ball seat made of synthetic resins or metals due to the rotation of the ball in writing operation, which leads to the so-called ball retraction of the ball-point pen. When such ball retraction occurs, ink guide grooves in a tip of the ball-point pen are blocked off with the thus retracted ball so that the ink is prevented from being sufficiently discharged, whereby scratchy line appears in writing to prevent a smooth writing operation from being performed. This is a problem inherent in the conventional water-based ink type ball-point pen.
In recent year, in order to resolve such problem, a certain attempt is made in which a water-soluble cutting oil is added to the water-based ink. However, such attempt fails to obtain a sufficient effect and produces another problem of a lateral penetration of the ink in the paper.